Treatment of tertiary butyl hydroperoxide distillation fraction to remove acidic contaminants

ABSTRACT

The distillation product fraction obtained from an isobutane oxidation reaction product after the removal of unreacted isobutane will contain tertiary butyl hydroperoxide, tertiary butyl alcohol and carboxylic acid contaminants such as formic acid, acetic acid and isobutyric acid. It has been discovered that when the distillation product fraction is treated with about 1/2 to 1 equivalents of calcium oxide and/or calcium hydroxide based on the carboxylic acid content of the distillate product fraction, a portion of the carboxylic acid contaminants will precipitate thus partially purifying the distillation product fraction so that, thereafter, molybdenum precipitation will be substantially inhibited when the thus-treated distillation product fraction is used as a feedstock for an epoxidation reaction wherein tertiary butyl hydroperoxide is reacted with an olefin in the presence of a soluble molybdenum catalyst to provide an olefin epoxide and additional tertiary butyl hydroperoxide.

This is a division of application Ser. No. 07/400,901, filed Aug. 30,1989, now U.S. Pat. No. 5,093,506.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for the treatment of a solution oftertiary butyl hydroperoxide in tertiary butyl alcohol to be used as afeedstock in a molybdenum catalyzed olefin epoxidation process in orderto inhibit precipitation of the molybdenum catalyst during theepoxidation reaction. More particularly, this invention relates to amethod for the partial removal of acidic impurities such as formic acid,acetic acid, isobutyric acid, etc., from a solution of tertiary butylhydroperoxide in tertiary butyl alcohol to be used as a feedstock in anolefin epoxidation process, such as a process wherein propylene iscatalytically reacted with tertiary butyl hydroperoxide in solution intertiary butyl alcohol in the presence of a catalytic amount of asoluble molybdenum compound in order to inhibit precipitation of themolybdenum catalyst during the epoxidation reaction.

More particularly, this invention relates to a method for thepretreatment with calcium hydroxide and/or calcium oxide of adistillation fraction to be used as a feedstock in a molybdenumcatalyzed olefin epoxidation process wherein tertiary butylhydroperoxide is reacted with an olefin, such as propylene, in solutionin tertiary butyl alcohol in an epoxidation reaction zone in order toprovide propylene oxide and additional tertiary butyl alcohol, thedistillation fraction comprising a solution of tertiary butylhydroperoxide in tertiary butyl alcohol contaminated with acidicimpurities such as formic acid, acetic acid, isobutyric acid, etc., theimprovement of the present invention comprising the pretreatment of thedistillation fraction with an amount of calcium oxide and/or calciumhydroxide sufficient to partially precipitate the acidic impurities andthe removal of the precipitate, whereby, when the thus-treateddistillation fraction is used as a feed stock in the epoxidationreaction process, the precipitation of the molybdenum catalyst duringthe epoxidation reaction is substantially inhibited.

2. Background of the Present Invention

When an olefin epoxide, such as propylene oxide, is to be prepared fromthe corresponding olefin, such as propylene, by reacting the olefin inorganic solvent solution with tertiary butyl hydroperoxide in thepresence of a soluble molybdenum catalyst, it is conventional practiceto prepare the hydroperoxide feedstock by the non-catalytic or catalyticoxidation of isobutane with oxygen in an oxidation reaction zone toprovide an oxidation reaction product comprising unreacted isobutane,tertiary butyl hydroperoxide, tertiary butyl alcohol andoxygen-containing impurities.

It is also conventional practice to remove the unreacted isobutane fromthe initial oxidation reaction product by distillation and to use theremaining distillation product fraction (normally a bottoms fraction) asthe feedstock for the molybdenum-catalyzed reaction of an olefin withthe tertiary butyl hydroperoxide. This is advantageous because thetertiary butyl alcohol present in the initial oxidation reaction productserves as a solvent for the peroxidation reaction and because theco-product of the peroxidation reaction is tertiary butyl alcohol,derived from the tertiary butyl hydroperoxide reactant. As aconsequence, product work-up is simplified because there is no need touse an extraneous solvent. Also, tertiary butyl alcohol is widely usedin motor fuels to enhance the octane characteristics of the motor fuels.

3. Prior Art

It is known to react propylene with tertiary butyl hydroperoxide in thepresence of a soluble molybdenum catalyst to provide a reaction productcomprising propylene oxide and tertiary butyl alcohol. See, for example,Kollar U.S. Pat. No. 3,350,422, Kollar U.S. Pat. No. 3,351,635, andRussell U.S. Pat. No. 3,418,340.

It is also known to prepare soluble molybdenum catalysts to catalyze thereaction as disclosed, for example, in Bonetti et al. U.S. Pat. No.3,480,563, Shum et al. U.S. Pat. No. 4,607,113, Marquis et al. U.S. Pat.No. 4,626,596, Marquis et al. U.S. Pat. No. 4,650,886, Marquis et al.U.S. Pat. No. 4,703,027, etc.

It has also been recognized in the prior art that it is desirable toconduct the molybdenum-catalyzed reaction between the propylene andtertiary butyl hydroperoxide in a reaction medium of reduced acidity.Thus, Kollar U.S. Pat. No. 3,350,422 states that it is advantageous touse basic substances such as alkali metal compounds or alkaline earthmetal compounds with the catalyst in order to reduce acidity. Similardisclosures are found in Kollar U.S. Pat. No. 3,351,635 and Russell U.S.Pat. No. 3,418,340.

Wu et al. U.S. Pat. No. 4,217,287 discloses a process wherein thereaction is conducted in the presence of barium oxide in order to"stabilize the catalyst". Becker U.S. Pat. No. 4,262,143 discloses arelated process for preparing ethyl benzene hydroperoxide. The ethylbenzene hydroperoxide is prepared by the oxidation of ethyl benzene withmolecular oxygen in the presence of a small amount of a hydroxide orsalt of sodium or potassium. In another process, Iwaki et al. U.S. Pat.No. 4,293,720 discloses a liquid phase process for the preparation ofaromatic peroxides by the liquid phase oxidation of an aromatic compoundcontaining a secondary alkyl group with molecular oxygen in the presenceof a basic aqueous solution of a copper compound catalyst which alsocontains cupric carbonate and an alkali metal carbonate and/or an alkalimetal bicarbonate.

Kollar U.S. Pat. No. 3,860,662 is directed to an improvement in hisbasic process relating to the recovery of alcohols from the reactionproduct, which product is stated to be of an acidic nature, wherein abasic material such as an alkali metal or alkaline earth metal compoundis added to the reaction mixture. Kollar U.S. Pat. No. 3,947,500discloses a method for treating the reaction product formed by thereaction of an organic hydroperoxide with an olefin wherein an organicalcohol is formed as a by-product. It is stated that the alcohol tendsto dehydrate and that to at least partially overcome this problem theoxidation reaction product is treated with an alkali metal or analkaline earth metal compound. Kollar states that the alkali metal oralkaline earth metal compound can be added to the epoxidation reactor orto the reaction product.

Sorgenti U.S. Pat. No. 3,573,226 discloses a method wherein amolybdenum-containing catalyst solution is prepared by incorporatingmetallic molybdenum into the distillate bottoms fraction of anepoxidation reaction product followed by heating of the resultantmixture in order to form a soluble molybdenum-containing reactionproduct which can be used to catalyze the epoxidation reaction.

The molybdenum-catalyzed epoxidation of alpha olefins and alphasubstituted olefins with hydroperoxides less stable than tertiary butylhydroperoxide may be accomplished according to U.S. Pat. No. 3,862,961to Sheng, et al. by employing a critical amount of a stabilizing agentconsisting of a C₃ to C₉ secondary or tertiary monohydric alcohol, suchas tertiary butyl alcohol. Citric acid is used to minimize theiron-catalyzed decomposition of the organic hydroperoxide withoutadversely affecting the reaction between the hydroperoxide and theolefin in a similar oxirane producing process taught by Herzog in U.S.Pat. No. 3,928,393. The inventors in U.S. Pat. No. 4,217,287 discoveredthat if barium oxide is present in the reaction mixture, the catalyticepoxidation of olefins with organic hydroperoxides can be successfullycarried out with good selectivity to the epoxide based on hydroperoxideconverted when a relatively low olefin to hydroperoxide mole ratio isused. The alpha-olefinically unsaturated compound should be addedincrementally to the organic hydroperoxide.

Selective epoxidation of olefins with cumene hydroperoxide (CHP) can beaccomplished at high CHP to olefin ratios if barium oxide is presentwith the molybdenum catalyst as reported by Wu and Swift in "SelectiveOlefin Epoxidation at High Hydroperoxide to Olefin Ratios," Journal ofCatalysis, Vol. 43, 380-383 (1976).

Maurin U.S. Pat. No. 3,931,076 is directed to a method for recoveringmolybdenum catalyst values from a peroxidation reaction product forrecycle. Maurin discloses one of three techniques. In accordance withthe first embodiment, the residue fraction is calcined to providemolybdenum trioxide which is then used to prepare a soluble molybdenumcompound by reaction with aqueous ammonia. In a second embodiment, themolybdenum-containing fraction is treated with aqueous ammonia withoutcalcining to form an ammonium molybdate which is treated with apolyalcohol to give a molybdic ester. In a third embodiment, themolybdenum-containing fraction is treated with gaseous ammonia in orderto form an ammonium molybdate precipitate which can be recovered byfiltration.

As can be seen by the foregoing, when it is desired to reutilize themolybdenum catalyst initially used to catalyze the epoxidation reactionbetween an olefin such as propylene and a hydroperoxide such as tertiarybutyl hydroperoxide, the used molybdenum catalyst is normallyconcentrated in a distillation bottoms fraction which contains otherimpurities such that direct recycle, without treatment, is normallyimpractical.

Harvey U.S. Pat. No. 3,449,217 is directed to a process for the recoveryof tertiary butyl hydroperoxide from a mixture comprising tertiary butylhydroperoxide, tertiary butyl alcohol and organic acids and estersresulting from the liquid phase oxidation of isobutane by a processwhich minimizes hydroperoxide decomposition. This is done byaccomplishing the distillation while the product has an effective pH ofbelow about 9. The patentee teaches the treatment of the reactoreffluent with a neutralizing agent such as an alkali metal or analkaline earth metal hydroxide.

SUMMARY OF THE INVENTION

It has been discovered in accordance with the present invention thatwhen a solution of tertiary butyl hydroperoxide in tertiary butylalcohol is treated with a conventional base, such as sodium hydroxide,sodium carbonate, sodium butoxide, potassium hydroxide, potassiumbutoxide, ammonium hydroxide, etc., precipitation of the solublemolybdenum catalyst used to catalyze the reaction of an olefin withtertiary butyl hydroperoxide in solution in tertiary butyl alcohol canunpredictably occur when the propylene and the soluble molybdenumcatalyst are added to a base-treated solution of tertiary butylhydroperoxide in tertiary butyl alcohol.

It has been further discovered, in accordance with the presentinvention, that the precipitation of the soluble molybdenum catalystfrom the solution of olefin and tertiary butyl hydroperoxide in solutionin tertiary butyl alcohol in the epoxidation reaction zone can besubstantially inhibited when a distillation fraction comprising asolution of tertiary butyl hydroperoxide in tertiary butyl alcohol whichis contaminated with acidic impurities such as formic acid, acetic acid,isobutyric acid, etc., is treated with calcium oxide and/or calciumhydroxide for the partial removal of such acidic impurities before thethe solution of olefin and tertiary butyl hydroperoxide in solution intertiary butyl alcohol is charged to the epoxidation reaction zone.

One aspect of the present invention is the treatment with calcium oxideand/or calcium hydroxide of a distillation fraction comprising asolution of tertiary butyl hydroperoxide in tertiary butyl alcoholcontaminated with carboxylic acid impurities in order to enhance theutility of the distillation fraction as a feed component for anepoxidation reaction.

Another aspect of the present invention is a process wherein isobutaneis charged to an oxidation reaction zone where it is reacted underoxidation reaction conditions with an amount of oxygen sufficient toprovide an oxidation reaction mixture comprising about 50 to 80 wt.% ofunreacted isobutane, together with tertiary butyl hydroperoxide,tertiary butyl alcohol and impurities, including about 1 wt.% or more ofcarboxylic acid impurities such as formic acid, acetic acid andisobutyric acid, wherein the oxidation reaction mixture is separated bydistillation into a distillate recycle isobutane fraction and a heavierdistillation fraction comprising the tertiary butyl hydroperoxide, thetertiary butyl alcohol and the carboxylic acid impurities, wherein theheavier distillation fraction is treated with about 1/2 to 1equivalents, based on the carboxylic acids, of calcium oxide and/orcalcium hydroxide to form a treated fraction containing a precipitateand wherein the precipitate is separated from the treated fraction toprovide a feed fraction comprising the tertiary butyl hydroperoxide, thetertiary butyl alcohol and a lesser quantity of the carboxylic acidimpurities.

Another aspect of the present invention is the epoxidation of an olefinwith tertiary butyl hydroperoxide in an epoxidation reaction zone underepoxidation reaction conditions in the presence of a catalytic amount ofa soluble molybdenum catalyst compound wherein the olefin and thesoluble molybdenum catalyst are added to a solution of tertiary butylhydroperoxide in tertiary butyl alcohol, the solution of tertiary butylhydroperoxide in tertiary butyl alcohol being a distillation fractioncomprising a solution of tertiary butyl hydroperoxide in tertiary butylalcohol containing about 1 to about 5 wt. % of C₁ to C₄ carboxylic acidimpurities that has been treated with calcium oxide and/or calciumhydroxide for the partial removal of carboxylic acid impuritiestherefrom before the olefin and the soluble molybdenum catalyst areadded thereto.

Yet another aspect of the present invention is a process wherein anolefin is reacted with tertiary butyl hydroperoxide in an epoxidationreaction zone in solution in tertiary butyl alcohol under epoxidationreaction conditions in the presence of a catalytic amount of a solublemolybdenum catalyst compound to provide an epoxidation reaction mixturecomprising unreacted propylene, propylene oxide, additional tertiarybutyl alcohol, tertiary butyl hydroxide, and carboxylic acid impuritiessuch as formic acid, acetic acid, isobutyric acid, etc., wherein theepoxidation reaction mixture is separated by distillation into adistillate recycle propylene fraction, a distillate propylene oxideproduct fraction, a distillate tertiary butyl alcohol product fractioncontaining about 1 to about 5 wt. % of C₁ to C₄ carboxylic acidimpurities and a heavier distillation fraction comprising tertiary butylalcohol, tertiary butyl hydroperoxide and impurities including themolybdenum catalyst, wherein the distillate tertiary butyl alcoholfraction is treated with about 1/2 to 1 equivalents of calcium oxideand/or calcium hydroxide, based on the carboxylic acid content of thedistillate fraction for the partial precipitation of the carboxylic acidimpurities therefrom, and wherein the thus-treated distillate fraction,after the removal of the precipitate therefrom, is recycled to theepoxidation reaction zone.

A preferred embodiment of the present invention is a process:

a. wherein isobutane is reacted with oxygen in an oxygenation reactionzone to form a reaction product comprising unreacted isobutane, tertiarybutyl alcohol, tertiary butyl hydroperoxide and oxygen-containingimpurities including di-tertiary butyl peroxide, acetone, methanol, andcarboxylic acid impurities including acetic acid, formic acid, andisobutyric acid,

b. wherein the reaction product is charged to a distillation zone whereit is separated into a lighter isobutane recycle distillate fraction anda heavier distillation fraction comprising a solution of at least a 30wt. % tertiary butyl hydroperoxide in tertiary butyl alcohol which iscontaminated with tertiary butyl peroxide, acetone, methanol, andcarboxylic acid impurities such as formic acid, acetic acid, isobutyricacid, etc.,

c. wherein said heavier distillation fraction is charged to a firsttreatment zone where it is reacted with about 1/2 to about 1 equivalentsof calcium oxide and/or calcium hydroxide, based on the carboxylic acidcontent of the heavier distillation fraction to form a slurry ofpartially precipitated carboxylic acid impurities,

d. wherein said slurry is charged to a separation zone and resolvedtherein into a solids fraction and a filtrate fraction comprising atertiary butyl alcohol solution of tertiary butyl hydroperoxide,

e. wherein said filtrate fraction comprising said tertiary butyl alcoholsolution of tertiary butyl hydroperoxide is charged to an epoxidationzone together with a soluble molybdenum catalyst and propylene,

f. wherein epoxidation reaction conditions are established in saidepoxidation reaction zone for the molybdenum catalyzed reaction of thepropylene with the tertiary butyl hydroperoxide contained in saidfiltrate fraction to form an epoxidation reaction product containingpropylene oxide and additional tertiary butyl alcohol, and

g. wherein propylene oxide and tertiary butyl alcohol are recovered fromthe said epoxidation reaction product.

A specific embodiment of the present invention is a process:

a. wherein isobutane is reacted with oxygen in an oxygenation reactionzone to form an oxidation reaction product comprising unreactedisobutane, tertiary butyl alcohol, tertiary butyl hydroperoxide andoxygen-containing impurities such as di-tertiary butyl peroxide,acetone, methanol, and carboxylic acid impurities including acetic acid,formic acid and isobutyric acid,

b. wherein the reaction product is charged to a first distillation zonewhere it is separated into a lighter isobutane recycle distillatefraction and a first heavier distillation fraction comprising at least a30 wt. % solution of tertiary butyl hydroperoxide in tertiary butylalcohol which is contaminated with tertiary butyl peroxide, acetone,methanol, and about 1 wt. % or more of carboxylic acid impurities suchas formic acid, acetic acid, isobutyric acid, etc.,

c. wherein the first heavier distillation fraction is charged to a firsttreatment zone where it is reacted with about 1/2 to 1 equivalents ofcalcium oxide and/or calcium hydroxide, based on the carboxylic acidcontent of the first heavier distillation fraction, to form a firstslurry of partially precipitated carboxylic acid impurities,

d. wherein the first slurry is charged to a first separation zone andresolved therein into a solids fraction and a first filtrate fractioncomprising a tertiary butyl alcohol solution of tertiary butylhydroperoxide containing a reduced quantity of carboxylic acids,

e. wherein the first filtrate fraction comprising the tertiary butylalcohol solution of tertiary butyl hydroperoxide is charged to anepoxidation zone together with a soluble molybdenum catalyst andpropylene,

f. wherein epoxidation reaction conditions are established in theepoxidation reaction zone for the molybdenum catalyzed reaction of thepropylene with the tertiary butyl hydroperoxide contained in the firstfiltrate fraction to form an epoxidation reaction product containingunreacted propylene, propylene oxide, additional tertiary butyl alcohol,unreacted tertiary butyl hydroperoxide and impurities, including about 1to about 5 wt. % of C₁ to C₄ carboxylic acid impurities such as formicacid, acetic acid, isobutyric acid, etc.,

g. wherein the epoxidation reaction product is charged to a seconddistillation zone where it is separated into a distillate propylenerecycle fraction, a distillate propylene oxide product fraction, adistillate tertiary butyl alcohol product fraction containing impuritiesincluding about 1 to about 5 wt. % of C₁ to C₄ carboxylic acid, tertiarybutyl hydroperoxide, etc., and a heavy distillation fraction comprisingtertiary butyl alcohol, unreacted tertiary butyl hydroperoxide andimpurities, including the molybdenum catalyst,

h. wherein the distillate tertiary butyl alcohol product fractioncontaining impurities including about 1 to about 5 wt. % of C₁ to C₄carboxylic acid, tertiary butyl hydroperoxide, etc., is reacted in atreating zone with about 1/2 to 1 equivalents of calcium oxide and/orcalcium hydroxide, based on the carboxylic acid content of the fractionbeing treated, to form a slurry of partially precipitated carboxylicacid impurities,

i. wherein the thus-formed slurry is charged to a separation zone andresolved therein into a solids fraction and a second filtrate fractioncontaining a reduced quantity of the carboxylic acid impurities.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, a principal aspect of the present invention is thediscovery that precipitation of the molybdenum catalyst in themolybdenum catalyzed epoxidation of an olefin with base-treated tertiarybutyl hydroperoxide is substantially eliminated when the distillationfraction used as one of the feed components for the epoxidation reaction(a solution of tertiary butyl hydroperoxide in tertiary butyl alcoholcontaminated with carboxylic acid impurities) is treated with about 1/2to about 1 equivalents of calcium oxide and/or calcium hydroxide, basedon the carboxylic acids in the distillation fraction to form calciumsalts of the carboxylic acids that can be removed by filtration beforethe distillation fraction is used in the epoxidation reaction. Thus, thecalcium oxide and/or calcium hydroxide treating step is one of theseveral steps involved in converting isobutane and propylene to tertiarybutyl alcohol and propylene oxide.

Oxidation of Isobutane

The first step in the integrated process for converting isobutane andpropylene to tertiary butyl alcohol and propylene oxide is the oxidationof isobutane with oxygen to provide tertiary butyl hydroperoxide for useas a reactant and tertiary butyl alcohol for use as a solvent.

The oxidation of isobutane with molecular oxygen is conducted in anoxidation reaction zone in liquid phase. It is not necessary to use anoxidation catalyst, although one is sometimes employed. The oxidation ispreferably conducted at a moderate pressure because of the volatility ofisobutane, such as a pressure of about 50 to 1,000 psig. The oxidationreaction is usually conducted at a temperature of about 40° to about200° C., such as a temperature of about 80° to about 180° C. and, morepreferably, from about 90° to about 150° C.; reaction time and reactionconditions being correlated to provide a desired conversion of theisobutane, such as a conversion of about 10 to about 75% and, morepreferably, from about 20 to about 50%. The composition of the oxidationreaction product is given in Table I.

The oxidation reaction product discharged from the oxidation reactionzone will normally have the composition shown in Table I.

                  TABLE I                                                         ______________________________________                                        COMPOSITION OF INITIAL OXIDATION REACTION                                     PRODUCT                                                                                      General       Preferred                                        Component      Range, Wt. %  Range, Wt. %                                     ______________________________________                                        Isobutane      25-90         50-80                                             .sub.- t-butyl hydroperoxide                                                                70-0          25-55                                             .sub.- t-butyl alcohol                                                                       0-70         25-55                                            Others*        0.5-10        0.5-5                                            ______________________________________                                         *Includes ditertiary butyl peroxide, acetone, methanol, acetic acid,          formic acid, isobutyric acid and other oxygenated impurities.            

The oxidation product is normally withdrawn from the oxidation reactionzone and charged to a first distillation zone where it is normallyseparated into a lighter unreacted isobutane fraction, which is suitablyrecycled to the oxidation reaction zone, and a heavier fractioncomprising tertiary butyl alcohol, tertiary butyl hydroperoxide andimpurities, including carboxylic acid impurities such as formic acid,acetic acid and isobutyric acid.

Calcium Oxide/Calcium Hydroxide Treatment

In accordance with the present invention, the heavy distillationfraction recovered in the first distillation zone after isobutaneoxidation is charged to a calcium oxide/calcium hydroxide treating zonewhere it is treated with calcium oxide and/or calcium hydroxide. It willbe understood that the treatment with calcium oxide and/or calciumhydroxide will be effective for partially removing acidic impurities,including carboxylic acid impurities but that other impurities such asacetone, methanol, etc., will not be significantly affected by thetreatment.

The heavy distillation fraction can be treated on a batch basis or on acontinuous basis under treating conditions including a temperature ofabout 25° to about 100° C. and a pressure of about 15 to about 500 psig.for a treating time of about 0.25 to about 300 hours in order to reactabout 1/2 to 1 equivalents of calcium oxide or calcium hydroxide, basedon the carboxylic acid content of the heavy distillation fraction withabout an equivalent amount of the carboxylic acid impurities in theheavy distillation fraction (e.g., formic acid, acetic acid, isobutyricacid) to form a slurry of precipitated calcium salts of the carboxylicacids in the heavy distillation fraction.

When the calcium oxide/hydroxide treatment is one step in a continuousprocess, as illustrated in the drawing, the treatment is preferablyconducted on a continuous basis in a treating vessel, such as anautoclave, equipped with an agitator and suitable temperature controlmeans, such as a cooling jacket. The autoclave treatment is preferablyconducted by continuously charging both the heavy distillation fractionand finely divided calcium oxide and/or calcium hydroxide to theautoclave at a temperature of about 75° to about 100 ° C., a pressure ofabout 100 to about 500 psig. for a treating time of about 0.25 to about5 hours in order to permit a substantial portion of the carboxylic acidimpurities in the heavy distillation fraction (e.g., formic acid, aceticacid, isobutyric acid) to react with the calcium oxide and/or calciumhydroxide to form a slurry of the precipitated calcium salts of thecarboxylic acids in the heavy distillation fraction. Again, about 1/2 toabout 1 equivalents of calcium oxide or calcium hydroxide should beused, based on the carboxylic acid content of the heavy distillationfraction.

The thus-formed slurry is charged to a separation zone containing anysuitable separating means such as a centrifugation means, filtrationmeans, etc., wherein the precipitate and other solids, if any, areseparated to provide a solids product and a filtrate comprising thetreated, partially purified solution of tertiary butyl hydroperoxide intertiary butyl alcohol.

Synthesis of Propylene Oxide and Tertiary Butyl Alcohol

The filtrate from the separation zone is charged to an epoxidation zonecontaining an epoxidation reactor to which an olefin such as an alphaolefin containing 3 to 10 carbon atoms, such as propylene is alsocharged. A molybdenum catalyst is also charged to the epoxidationreactor, preferably in admixture with the base-treated filtratecomprising the tertiary butyl alcohol solution of tertiary butylhydroperoxide. An epoxidation reaction is conducted in the epoxidationreactor under epoxidation reaction conditions in order to convert theolefin to the corresponding olefin epoxide and the tertiary butylhydroperoxide to tertiary butyl alcohol.

Under ambient conditions t-butyl hydroperoxide is a comparatively stablematerial. However, as the temperature increases, the hydroperoxide tendsto become "destabilized" so that thermal and/or catalytic decompositionwill be initiated leading to the formation of unwanted by-products suchas ketones, lower molecular weight alcohols, tertiary alcohols, oxygen,etc. This is a particularly troublesome problem at temperatures of 50°to 180° C. (e.g., 100° to 130° C.) which are normally used when tertiarybutyl hydroperoxide is catalytically reacted with an olefin to form anolefin epoxide. This problem can be at least partially overcome byconducting the epoxidation reaction in the presence of an excess of theolefin reactant. The unreacted olefin must be separated from the epoxidereaction product for recycle.

Epoxidation Reactants and Catalysts a) The Olefin

The method of this invention can be used to epoxidize C₃ -C₁₀olefinically unsaturated compounds such as substituted and unsubstitutedaliphatic and alicyclic olefins. The process is particularly useful inepoxidizing compounds having at least one double bond situated in thealpha position of a chain or internally. Representative compoundsinclude propylene, normal butylene, isobutylene, pentenes, methylpentenes, hexenes, octenes, dodecenes, cyclohexene, substitutedcyclohexenes, butadiene, styrene, substituted styrenes, vinyl toluene,vinyl cyclohexene, phenyl cyclohexenes and the like.

The invention finds its greatest utility in the epoxidation of propyleneand propylene is epoxidized particularly advantageously by the inventiveprocess.

The selectivity to olefin epoxide, on the basis of hydroperoxideconverted, can be enhanced when the hydroperoxide is charged to thereaction zone in at least a 30 wt. % solution of the correspondingproduct alcohol and the olefin is charged to the reaction zone in anamount relative to the hydroperoxide charged to the reaction zone suchthat about 0.9 to 2 moles of olefin are charged per mole ofhydroperoxide charged.

b) The Tertiary Butyl Hydroperoxide

The TBHP should be charged in at least a 30 wt. % solution in t-butylalcohol, and preferably about a 40 to 75 wt. % solution.

c) The Molybdenum Catalyst

Catalysts suitable for the epoxidation method of this invention aremolybdenum catalysts that are soluble in the reaction medium.

Examples of suitable soluble catalysts include molybdenum compounds suchas molybdenum octoate, molybdenum naphthenate, molybdenum acetylacetonate, molybdenum/alcohol complexes, molybdenum/glycol complexes,etc.

Other catalysts found to be useful are the molybdenum complexes ofalkylene glycols with molybdenum compounds as described in U.S. Pat. No.4,626,596 issued Dec. 12, 1986 and entitled "Improved Synthesis ofMolybdenum/Alkylene Glycol Complexes Useful as Epoxidation Catalysts".Briefly, these complexes are made by reacting an ammonium-containingmolybdenum compound with an alkylene glycol in the presence of water atan elevated temperature, such as about 80° to 130° C. Theammonium-containing molybdenum compound is preferably ammoniumheptamolybdate tetrahydrate or ammonium dimolybdate hydrate. Thealkylene glycols are preferably ethylene glycol and/or propylene glycolalthough others have been found to be useful.

Still other catalysts found to be useful in the practice of the presentinvention are molybdenum complexes of monohydric alcohols as describedin U.S. Pat. No. 4,650,886 issued Dec. 2, 1986 and entitled "ImprovedSynthesis of Molybdenum/Alcohol Complexes useful as EpoxidationCatalysts". Briefly, an alkanol such as 2-ethyl hexanol is reacted witha molybdenum oxide in the presence of ammonium hydroxide or by reactingthe alkanol with ammonium heptamolybdate in the presence of a controlledamount of water.

d) Epoxidation Reaction Conditions

The epoxidation reaction may be conducted at a temperature in the rangeof 50°-180° C. with a preferred range of between 90° and 140° C. Anespecially preferred range is 100° to 130° C. with about 110° C.-120° C.being the most preferred single stage operating temperature.

The catalyst concentrations in the method of this invention should be inthe range of 50 to 1,000 ppm (0.01 to 0.10 wt. %) based on the totalreactant charge. Catalyst concentration is calculated as molybdenummetal. A preferred range is 200 to 600 ppm. Generally, about 250-500 ppmis the most preferred level.

It has been discovered that the method of the present invention providesa process wherein the molybdenum catalyst is retained in solution in thepresence of a base-treated solution of tertiary butyl hydroperoxide intertiary butyl alcohol during the life of the reaction.

The epoxidation reaction of this invention is carried out in thepresence of a polar solvent.

Tertiary butyl hydroperoxide and TBA are coproduced commercially by theoxidation of isobutane, as noted, and tertiary butyl alcohol iscoproduced with the TBHP and will normally supply all of the polarsolvent required for the present invention.

It is preferred that the solution of TBHP in TBA contain very littlewater, between zero and 1 wt. %. Preferably, the water level should beless than 0.5 wt. %.

The reaction can be carried out to achieve a hydroperoxide conversionwhile still maintaining high epoxide selectivities, basis thehydroperoxide reacted. This is important because the profitability of acommercial olefin epoxide plant, to a significant extent, is increasedas the yield of olefin epoxide increases.

The reaction time may vary considerably, from minutes to hours.Generally, the reaction, times run from thirty minutes to three or fourhours with 1.5-2.0 hours being about average. The preferred single stagereaction time/temperature is two hours at 110° -120° C. Preferably thereaction is conducted in two or more temperature stages.

The reaction procedure generally begins by charging the olefin to thereaction vessel. Next, the hydroperoxide, polar solvent and catalyst maybe added and the contents heated to the desired reaction temperature.Alternatively, the olefin reactant may be heated to, at or near thepreferred reaction temperature, and then the hydroperoxide, polarsolvent and catalyst may be added. Further heat may be provided by theexotherm of the reaction. The reaction is then allowed to proceed forthe desired amount of time at the reaction temperature, generally110°-120° C., or conducted for 1 hour at 50°-120° C. followed by 1 hourat 120°-150° C. The mixture is cooled down and the oxide recovered.

A series of reactors helps to achieve the objectives of the presentinvention.

A more effective approach is to use a CSTR or a series of CSTR'sfollowed by one or more plug flow reactors because conversion can bemore effectively forced to completion in a plug flow reactor.

The epoxidation reaction product, which will comprise unreactedpropylene, unreacted tertiary butyl hydroperoxide, propylene oxide,tertiary butyl alcohol, and impurities, is withdrawn from theepoxidation reactor and charged to a distillation zone where it isresolved in one or a plurality of serially connected distillationcolumns into a plurality of distillate fractions, including a distillatepropylene recycle fraction, a product propylene oxide fraction, aproduct tertiary butyl alcohol fraction and a residual fractioncontaining unrecovered tertiary butyl hydroxide, unrecovered tertiarybutyl alcohol, the molybdenum epoxidation catalyst and impurities.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a schematic flow sheet with conventional parts omittedshowing the general reaction and recovery sequence that is used in thepractice of the preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawing, there is shown a schematic flow sheetillustrating a preferred method for the continuous practice of theprocess of the present invention. In the drawing, conventional partssuch as valves, pumps, temperature sensors, pressure sensors, heaters,coolers, control and flow regulation apparatus, reboilers, refluxcondensers, etc., have been omitted.

In accordance with a preferred embodiment of the present invention, anoxidation reactor 10 is provided with an oxygen charge line 12 and anisobutane charge line 14. Within the oxidation reactor 10, oxidationreaction conditions, such as a temperature of about 90° to about 150° C.and a pressure of about 50 to about 1,000 psig. are established in orderto bring about an oxidation of a portion of the isobutane fed by thecharge line 14, so as to obtain a conversion of the isobutane of, forexample about 20 to about 50%. As a consequence, a reaction mixture willbe formed within the oxidation reaction zone 10 comprising unreactedisobutane, tertiary butyl hydroperoxide, tertiary butyl alcohol andby-products including materials such as di-tertiary peroxide, acetone,methanol, and carboxylic acids such as formic acid, acetic acid andisobutyric acid, as shown in Table I above.

A stream of the oxidation reaction product is withdrawn from theoxidation reaction zone 10 by a line 16 leading to a first distillationzone comprising, for example, a distillation column 20 wherein theoxidation reaction product is separated into a lighter isobutanedistillate fraction 22 that may suitably be recycled to the isobutanecharge line 14 and a heavier distillation fraction discharged by a line21 comprising a tertiary butyl alcohol solution of tertiary butylhydroperoxide and by-products, including C₁ to C₄ carboxylic acids.

The heavy distillation fraction 21 is routed to a tertiary butylhydroperoxide drying distillation column 23 where the tertiary butylhydroperoxide is further concentrated and dried, being separated into adistillate tertiary butyl alcohol fraction 25 and a heavier driedsolution of tertiary butyl hydroperoxide in tertiary butyl alcohol whichis normally contaminated with C₁ to C₄ carboxylic acids and otheroxygenated impurities.

In accordance with the present invention, and especially when the heavydistillation fraction 24 has a carboxylic acid content of more thanabout 1 wt. % (e.g., about 1 to about 10 wt. %), valve 28 and valve 29will be closed and the valve 26 will be opened so that the heavierdistillation fraction in the line 24 is charged to a neutralizationzone, such as an autoclave 208 equipped with suitable agitation means.About 1/2 to about 1 equivalents of powdered calcium oxide and/orcalcium hydroxide, based on the carboxylic acids contained in theheavier distillation fraction 24, is also charged to the autoclave 208by a charge line 34. In this situation, wherein a continuousneutralization is to be accomplished, it is desirable to continuouslyfeed the calcium oxide and/or calcium hydroxide to the autoclave 208 inorder to maintain a level of about 1/2 to 1 equivalents of the calciumoxide or calcium hydroxide per equivalent of the carboxylic acids.

As a consequence, a slurry of the powdered calcium compound in theheavier fraction is formed, and is thoroughly mixed. Appropriateneutralization conditions are established in the autoclave 208, such asa temperature of about 70° to about 100° C., a residence time of about1/4 to about 5 hours, and an appropriate pressure, such as a pressure ofabout 100 to about 500 psig. As a consequence, the calcium oxide and/orcalcium hydroxide will partially react with the carboxylic acids presentin the autoclave 208 to form a precipitate. The resultant slurry isdischarged from the autoclave 208 by an autoclave discharge line 210.

By way of example, about 100 pounds per hour of the heavier distillationfraction 24 containing about 42-43 wt. % of tertiary butyl alcohol,about 55-56 wt. % of tertiary butyl hydroperoxide and about 0.7 to about0.8 wt. % of carboxylic acids is charged by the line 24 and treated inthe autoclave 208, as described with about 0.37 pound per hour ofcalcium hydroxide and for an average residence time of about 1 to about5 hours at a temperature of about 70° to about 100° C. and a pressure ofabout 100 to about 500 psig. and the resultant precipitate in thepartially purified tertiary butyl alcohol solution of tertiary butylhydroperoxide is discharged by a discharge line 210.

The slurried precipitate in the line 210 is charged to a separation zonecomprising, for example, a centrifuge 220 wherein the slurry isseparated into a solids fraction comprising calcium salts ofprecipitated carboxylic acids which is discharged by a line 222 and afiltrate fraction comprising a partially purified tertiary butyl alcoholsolution of tertiary butyl hydroperoxide which is discharged by a line224 leading to a holding tank 230, from which it can be recycled to theepoxidation reactor.

The epoxidation zone may comprise, by way of illustration, a reactor 50.The filtrate from holding tank 230 may proceed to a return tank 240 andthen through line 242, through valve 28 and line 52 to be charged to theepoxidation reactor 50 together with a soluble molybdenum catalyst suchas, for example, an ethylene glycol solution of an ethyleneglycol/molybdenum complex formed by the reaction of ethylene glycol withammonium heptamolybdate as shown, for example, in Marquis et al. U.S.Pat. No. 4,626,596. The catalyst solution may be added by supply line 51to the epoxidation reactor. The calcium oxide/calcium hydroxide treatedsolution of tertiary butyl hydroperoxide in tertiary butyl alcohol willbe charged to epoxidation reactor 50 via line 52. Only minimalprecipitation of the molybdenum catalyst, if any, will be experiencedbecause of the pretreatment of the partially purified tertiary butylalcohol solution of tertiary butyl hydroperoxide with calcium oxideand/or calcium hydroxide in the neutralization zone 208. Propylene isadded to the epoxidation reactor 50 through a propylene charge line 54,preferably in an amount such that a molar excess of olefin is chargedrelative to the charge of tertiary butyl hydroperoxide, e.g., propylenemay be charged at a rate of from about 1.5 to about 5 moles of propyleneper mol of tertiary butyl hydroperoxide charged.

Within the reactor 50 at least a portion of the propylene and at least aportion of the tertiary butyl hydroperoxide catalytically react to formadditional tertiary butyl alcohol and propylene oxide and to provide areaction product comprising unreacted propylene, propylene oxide,tertiary butyl alcohol, tertiary butyl hydroperoxide, andoxygen-containing impurities including C₁ to C₄ carboxylic acids such asformic acid, acetic acid, isobutyric acid, etc.

A stream of the reaction product is withdrawn from the reactor 50 by wayof a discharge line 56 leading to the primary fractionator 60. It willbe understood that the distillation zone may comprise a single column inwhich the several fractions are recovered as an overhead fraction orsidestream fractions, or as a plurality of splitter columns as shownschematically in the drawing. The discharge stream 56 is charged to theprimary fractionation column 60 where a distillate fraction comprisingpropylene and propylene oxide is taken overhead by a line 61. Theoverhead fraction 61 is fed to the propylene recycle distillation zone70. A propylene distillate fraction 62 is recycled from the propylenerecycle distillation zone 70 to the line 54 leading to the epoxidationreactor 50. A heavier crude propylene oxide distillation fraction 72 isdischarged from the propylene recycle distillation zone 70 for furthertreatment in a propylene oxide purification zone (not shown).

The bottoms fraction 74 from the primary fractionator 60 is charged to adistillation column 80 wherein an overhead distillate composed primarilyof tertiary butyl alcohol leaves via line 82. The tertiary butyl alcoholdistillate fraction 82 remains contaminated with contaminants includingC₁ to C₄ carboxylic acids and other oxygenated impurities. The bottomsfraction 84 from distillation column 80 is charged to an evaporationzone 200.

The distillate tertiary butyl alcohol fraction in line 82 may berecovered as a product. However, it is sometimes desirable to recyclethe fraction in line 82 to the epoxidation reactor 50 in order tomaintain a properly diluted solution of tertiary butyl hydroperoxidetherein. However, although the distillation column 80 is preferablyoperated to provide a cut point such the acidic impurities charged tothe distillation column 80, including carboxylic acids containing 1 to 4carbon atoms, will be concentrated in the bottoms fraction 84, there isa tendency due to azeotrope formation, distillation column upsets, etc.for the acidic impurities to azeotrope with the tertiary butyl alcoholor to otherwise become entrained therewith so that the distillatetertiary butyl alcohol fraction 82 will be contaminated with about 1 wt.% to 5 wt. % of carboxylic acids and to thus be unsuitable for recycleto the epoxidation reaction zone 50.

In this situation, the valve 83 may be partially or wholly closed andall or a part of the contaminated distillate tertiary butyl alcoholfraction 82 may be routed by a branch line 85 controlled by a valve 29to a neutralization zone 208 which may comprise an autoclave equippedwith suitable agitation means and to which about 1/2 to about 1equivalents of powdered calcium oxide and/or calcium hydroxide, based onthe carboxylic acids contained in the contaminated distillate tertiarybutyl alcohol fraction 82 is charged by way of a charge lines 85 and 34.Again, since a continuous neutralization is to be accomplished, thecalcium oxide and/or calcium hydroxide is continuously fed to theautoclave 208 in order to maintain a level of 1/2 to 1 equivalents ofthe calcium oxide or calcium hydroxide per equivalent of the carboxylicacids.

Appropriate neutralization conditions are established in the autoclave208, as described above, such as a temperature of about 70° to about100° C., a residence time of about 1/4 to about 5 hours, and anappropriate pressure, such as atmospheric pressure. As a consequence,the calcium oxide and/or calcium hydroxide will partially react with thecarboxylic acids present in the autoclave 208 to form a precipitate. Theresultant slurry is discharged from the autoclave 208 by an autoclavedischarge line 210.

The slurried precipitate in the line 210 is charged to a separation zonecomprising, for example, a centrifuge 220 wherein the slurry isseparated into a solids fraction comprising calcium salts ofprecipitated carboxylic acids which is discharged by a line 222 and asecond filtrate fraction comprising partially purified tertiary butylalcohol which is discharged by a line 224.

As indicated, the distillation column 80 is preferably operated so thata maximized amount of the acidic impurities discharged from theepoxidation reaction zone 50, including carboxylic acids containing 1 to4 carbon atoms, will be concentrated in the bottoms fraction dischargedby line 84.

The bottoms fraction 84 will normally contain tertiary butyl alcohol,unreacted tertiary butyl hydroperoxide, oxygenated impurities includingC₁ to C₄ carboxylic acids, the molybdenum catalyst, etc., and is chargedto an evaporation zone 200 where a solution of tertiary butylhydroperoxide in tertiary butyl alcohol is taken overhead by a line 204leading to a charge line 205 for neutralization zone 208. The bottomsfraction 202 from the evaporator 200 is a residue fraction that willtypically have the composition shown in Table II.

                  TABLE II                                                        ______________________________________                                        COMPOSITION OF RESIDUE FRACTION                                               Component       Concentration, Wt. %                                          ______________________________________                                         .sub.- t-butyl hydroperoxide                                                                 40-45                                                          .sub.- t-butyl alcohol                                                                       45-40                                                         Residue, including                                                                            10-15                                                         C.sub.1 -C.sub.4 carboxylic acids                                             Molybdenum, ppm   500-5,000                                                   ______________________________________                                    

From the table, it will be seen that the bottoms fraction 84 is highlycontaminated and not ameanable to separation into pure tertiary butylalcohol and tertiary butyl hydroperoxide fractions by conventionaldistillation techniques. However, in accordance with the presentinvention, a usable stream comprising a mixture of tertiary butylalcohol and tertiary butyl hydroperoxide can be obtained by routing thebottoms fraction 84 to an evaporation zone 200, comprising, for example,a wiped film evaporator wherein the bottoms fraction 84 is resolved intoa residue fraction that is discharged from the wiped film evaporator 200by a discharge line 202 and a condensate fraction discharged from thewiped film evaporator by a line 204. The condensate fraction 204 willnormally be contaminated with significant quantities of acidic materialsincluding, for example, from about 1 to about 10 wt. % of carboxylicacids containing 1 to 4 carbon atoms.

In accordance with the present invention, the condensate fraction 204may be routed via line 205 to a neutralization zone 208 constructed andoperated as described above. The condensate fraction 204 is continuouslycharged to the autoclave 208 via line 205 together with about 1/2 toabout 1 equivalents of powdered calcium oxide and/or calcium hydroxide,based on the carboxylic acids contained in the contaminated condensatefraction 204, the calcium oxide and/or calcium hydroxide beingcontinuously charged to the autoclave 208. Appropriate neutralizationconditions are established in the autoclave 208, as described above,such as a temperature of about 70° to about 100° C., a residence time ofabout 1/4 to about 5 hours, and an appropriate pressure, such asatmospheric pressure. As a consequence, the calcium oxide and/or calciumhydroxide will partially react with the carboxylic acids present in theautoclave 208 to form a precipitate. The resultant slurry is dischargedfrom the autoclave 208 by an autoclave discharge line 210 leading to thecentrifuge 220 wherein the slurry is separated into a solids fractioncomprising calcium salts of precipitated carboxylic acids which isdischarged by a line 222 and a filtrate fraction comprising a partiallypurified stream of tertiary butyl alcohol and tertiary butylhydroperoxide which is discharged by a line 224 to a holding tank 230.This treated material may be routed through return tank 240 to theepoxidation reactor 50 via line 242.

EXAMPLES

The invention will be further illustrated by the following specificexamples which are laboratory experiments that were conducted in amanner to verify the discoveries that have been made. Accordingly,precisely controlled amounts of base were used. The neutralizationreactions were conducted in glass bottles at atmospheric pressure (andtherefore had to be conducted at room temperature) for prolonged periodsof time to make sure that the reactions went substantially tocompletion. It will be understood, as illustrated above, that inconducting a continuous process larger quantities of the calcium oxideand/or calcium hydroxide could be used and the reactions would beconducted over significantly shorter reaction periods at elevatedtemperatures.

EXAMPLE 1 (6333-11)

To a pint bottle was added 300.0 g of peroxidate* solution (obtained byisobutane oxidation and containing 55.48% of tertiary butylhydroperoxide (TBHP), having an acid number of 11.08 mg KOH/g, and aformic acid content of 0.56 wt. % formate, and an acetic acid content of0.18 wt. % acetate, and 0.07% isobutyrate) followed by 3.14 g ofanhydrous Na₂ CIO₃ (MW 106, 0.0296 mols, 0.0592 equivalents of base).This slurry was stirred for four days at room temperature and filtered.The filtrate contained 54.74% TBHP, had an acid number of 0.65 mg KOH/gand had a formate content of 0.02 wt. %, acetate=0.13 wt. % andisobutyrate=0.10 wt. %. The filtered base treated peroxidate (164.41 g)was stirred with 0.442 g of a fresh catalyst comprising an ethyleneglycol solution of a molybdenum/ethylene glycol complex containing 13.0% moly (moly-EG catalyst 5990-32-2). Based on a total weight of 164.852g (164.41+0.442 g) the expected molybdenum (moly) level was 349 ppm.After stirring for two days at room temperature, the hazy solution wasfiltered and the filtrate analyzed for ppm moly and found to containonly 79.0 ppm moly or 22.6% of that charged. The peroxidate treated withNa₂ CO₃ caused precipitation of the majority of the soluble molybdenumcatalyst charged.

*300.0 Grams of peroxidate contained 0.059251 mole acid basis theobserved acid number of 11.08.

EXAMPLE 2 (6333-12)

To a pint bottle was added 300.0 g of peroxidate (same as in Example 1)and 1.66 g of anhydrous KOH (MW 56.1, 0.0296 mols). This clear solutionwas stirred for four days at room temperature and was analyzed and foundto contain 53.57% TBHP, acid number of 4.86, and formate content was0.44 wt%, acetate was 0.20 wt. % and isobutyrate was 0.06 wt. %. Thebase treated peroxidate (168.00 grams) was stirred with 0.449 g ofmoly-EG catalyst 5990-39-2 (13.0% moly). Based on total weight of168.559 g the expected moly level was 346 ppm. After stirring two daysat room temperature the hazy solution was filtered and analyzed and thefiltrate found to contain only 16 ppm moly or 4.6% of that charged. Thebase treated peroxidate caused precipitation of nearly all of themolybdenum charged.

EXAMPLE 3 (6333-13)

To a pint bottle was added 300.0 g of peroxidate (same as in Example 1)and 1.19 g of anhydrous NaOH (MW 40, 0.0298 mols). The hazy solution wasstirred for four days at room temperature and was filtered. The filtratewas analyzed and found to contain 53.34% TBHP, acid number of 4.82, andformate content of 0.12 wt. %, acetate was 0.21 wt. % and isobutyratewas 0.12 wt. %. The base treated filtrate (168.73 g) was stirred with0.450 g of moly-EG catalyst 5990-39-2 (13.0% moly). Based upon totalweight of 169.18 g the expected moly level was 346 ppm. After stirring 2days at room temperature, the hazy solution was filtered and thefiltrate analyzed and found to contain 210 ppm moly or 60.7% of thatcharged. The base-treated peroxidate caused precipitation of nearly 40%of the molybdenum charged.

EXAMPLE 4 (6333-14)

To the peroxidate described in Example 1 (300.0 grams) was added 3.30 gof anhydrous potassium t-butoxide and 46.7 g of t-butyl alcohol (MW ofKOtBu=112.1, 0.0294 mols added). The clear solution was stirred for fourdays at room temperature and was found to contain 46.57% TBHP (97.1% ofthat charged, 46.5% of 350.0g), acid number of 3.94, formate=0.39 wt. %,acetate=0.17 wt. %, and isobutyrate=0.13 wt. %. The base treatedfiltrate (193.26 g) was stirred with 0.497 g of moly-EG catalyst5990-39-2 (13.0% moly). Based upon a total weight of 193.57 g theexpected moly level was 333 ppm. After stirring for 2 days at roomtemperature the hazy solution was filtered and the filtrate analyzed formoly and found to contain <10 ppm or less than 3.0% of the moly charged.The base treated peroxidate caused precipitation of more than 97% of themolybdenum charged.

EXAMPLE 5 (6333-15)

To the peroxidate described in Example 1 (300.0 g) was added 2.85 g ofanhydrous sodium t-butoxide and 197.15 g of t-butyl alcohol (MW ofNaOtBu=97, 0.0297 mols). The hazy solution was stirred for four days atroom temperature and was filtered. The filtrate was analyzed and foundto contain 32.69% TBHP (97.8% of that charged, 32.69%×500.0 g), acidnumber of 3.56, formate=0.07 wt. %, acetate=0.13 wt. %, andisobutyrate=0.08 wt. %. The base treated filtrate 275.31 g was stirredwith 0.654 g of moly-EG catalyst 5990-39-2 (13.0% moly). Based on atotal weight of 275.964 g the expected moly level was 308 ppm. Afterstirring for two days at room temperature, the hazy, solution wasfiltered and the filtrate analyzed for molybdenum and found to contain160 ppm or 51.9% of the moly charged. The base-treated peroxidate causedprecipitation of nearly half of the moly charged

EXAMPLE 6 (6333-34)

To the peroxidate described in Example 1 (300.0 g) was added 1.75 g ofconcentrated ammonium hydroxide solution (28.8% NH₃, 0.504 g NH₃, 0.0296mols NH₃). The clear solution was stirred for 12 days at roomtemperature and was analyzed and found to contain 53.77% TBHP and anacid number of 8.77 mg KOH/g sample. To the clear base-treatedperoxidate (168.00 g) was added 0.44 g of moly-EG catalyst (5990-39-2,moly=13.0%). The cloudy mixture, with some precipitate visible, wasstirred for two days at room temperature and was filtered. The filtratewas analyzed and found to contain only 14 ppm molybdenum or only 4.1% ofthat charged (expected moly in solution was 340 ppm). The base-treatedperoxidate again caused precipitation of nearly all of the molybdenumcharged. The filtrate was also analyzed for TBHP=54.55%, acidnumber=7.77 mg KOH/g, formate=0.31 wt. %, acetate=0.20 wt. %, andisobutyrate=0.14 wt. %.

EXAMPLE 7 (6333-35)

To the peroxidate described in Example 1 (300.0 g) was added 1.10 g ofCa(OH)₂ (0.0148 mols, 0.0296 equivalents). The slurry was stirred for 12days at room temperature and filtered. The filtrate was found to contain53.95% TBHP, and an acid number of 5.10 mg KOH/g sample. To the basetreated filtrate (164.0 g) was added 0.44 g of moly-EG catalyst5990-39-2 (13.0% moly). Based on a total weight of 164.44 g the expectedmoly level was 348 ppm. The slightly hazy solution was stirred for twodays at room temperature and filtered. The filtrate was analyzed and wasfound to contain 349 ppm moly (100.3% of the moly charged), 53.99% TBHP,acid number of 4.95 mg KOH/g and a formate content of 0.07 wt. %,acetate=0.20 wt. % and isobutyrate=0.13 wt. %. Here, the base-treatedperoxidate had the acidity reduced (by about 50%) but did notprecipitate the moly catalyst as was observed in all other previousexamples.

EXAMPLE 8 (6333-36)

To the peroxidate described in Example 1 (300.0 g) was added 0.83 g CaO(0.0148 mols, 0.0296 equivalents). The slurry was stirred for 12 days atroom temperature and filtered. The filtrate was found to contain 53.81%TBHP, and an acid number of 7.64 mg KOH/g. To the base treated filtrate(166.0 g) was added 0.44 g of moly EG catalyst 5990-39-2 (13.0% moly).Based on a total weight of 166.44 g the expected moly level was 344 ppm.The slightly hazy solution was stirred for two days at room temperatureand was filtered. The filtrate was analyzed and was found to contain 349ppm moly (101.4% of the moly charged), 53.61% TBMP, an acid number of8.85 mg KOH/g sample, and a formate content of 0.23 wt. %, acetate=0.20wt. %, and isobutyrate=0.13 wt. %. Here, again the base-treatedperoxidate did not precipitate molybdenum as did the previous basesexamined in Examples 1-6. The CaO described in this example did notremove acidity as efficiently as Ca(OH)₂ described above in Example 7,but like the Ca(OH)₂ did not cause molybdenum precipitation.

A summary of the data (results) from Examples 1-8 is presented in TablesIII-A and III-B, attached.

                                      TABLE III-A                                 __________________________________________________________________________    TREATMENT OF PILOT PLANT PEROXIDATE DISTILLATION BOTTOMS WITH VARIOUS         BASES TO                                                                      DETERMINE WHICH BASES REDUCE ACIDITY AND WHICH ACIDS, IF ANY, ARE REMOVED     BY BASE                                                                       TREATMENT. ALSO, ADDITION OF MOLYBDENUM TO THE BASE-TREATED PEROXIDATES       TO SEE IF                                                                     MOLYBDENUM IS SOLUBLE.                                                                                        7    8                                                                    6   Grams                                                                              Grams                                                                              9                                         2    3      4    5    Equiv                                                                             Formate                                                                            Acetate                                                                            Grams    10    11                         NB # of                                                                            Reaction                                                                             Grams                                                                              G Moles                                                                            Base/                                                                             Charged                                                                            Charged                                                                            Isobutyrate Chgd                                                                       Base  Base                 1     the Feed                                                                           Conditions                                                                           TBHP Acid Equiv                                                                             to the                                                                             to the                                                                             to the   Charged                                                                             Charged              NB Run #                                                                            Charged                                                                            Time   Charged                                                                            Charged                                                                            Acid                                                                              Peroxide                                                                           Peroxide                                                                           Peroxide (Grams)                                                                             Equiv                __________________________________________________________________________    6333-11                                                                             6333-4-1                                                                           RT 96 hrs                                                                            166.44                                                                             .059251                                                                              1/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   NA.sub.2 CO.sub.3                                                                   NA.sub.2                                                                      CO.sub.3                                                                (3.14)                                                                              0.0592               6333-13                                                                             6333-4-1                                                                           RT 96 hrs                                                                            166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   NAOH  NAOH                                                                    (1.19)                                                                              0.0298               6333-15                                                                             6333-4-1                                                                           RT 96 hrs                                                                            166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   NAOTBU                                                                              NAOTBU                                                                  (2.85)                                                                              0.0297               6333-12                                                                             6333-4-1                                                                           RT 96 hrs                                                                            166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   KOH   KOH                                                                     (1.66)                                                                              0.0296               6333-14                                                                             6333-4-1                                                                           RT 96 hrs                                                                            166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   KOTBU KOTBU                                                                   (3.30)                                                                              0.0294               6333-34                                                                             6333-4-1                                                                            RT 288 hrs                                                                          166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   NH.sub.4 OH                                                                         NH.sub.4 OH                                                             (0.504)*                                                                            0.0296               6333-35                                                                             6333-4-1                                                                            RT 288 hrs                                                                          166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   CA(OH).sub.2                                                                        CA(OH).sub.2                                                            (1.10)                                                                              0.0296               6333-36                                                                             6333-4-1                                                                            RT 288 hrs                                                                          166.44                                                                             .059251                                                                            0.5/1                                                                             1.6800                                                                             0.5400                                                                             0.2100   CAO   CAO                                                                     (0.83)                                                                              0.0296               __________________________________________________________________________     Amount of feed 300 grams for all runs                                         6333-4-1 = Pilot plant peroxide distillation bottoms, TBHP = 55.48 wt. %      RT = Room temperature                                                         *Grams NH.sub.3                                                               In the basetreated peroxidates where solids formed upon base treatment,       the solids were filtered before moly was added.                          

                                      TABLE III-B                                 __________________________________________________________________________    TREATMENT OF PILOT PLANT PEROXIDATE DISTILLATION BOTTOMS WITH VARIOUS         BASES TO                                                                      DETERMINE WHICH BASES REDUCE ACIDITY AND WHICH ACIDS, IF ANY, ARE REMOVED     BY BASE                                                                       TREATMENT. ALSO, ADDITION OF MOLYBDENUM TO THE BASE-TREATED PEROXIDATES       TO SEE IF                                                                     MOLYBDENUM IS SOLUBLE.                                                                                                            20                                               15          17    18   19    % of MO                         12               TBHP in                                                                             16    Acid in                                                                             ppm  After Fed that                        Grams                                                                              13    14    Liquid                                                                              G Moles                                                                             Liquid                                                                              Moly Stirring &                                                                          Remains                         Solvent                                                                            Physical                                                                            G TBHP                                                                              After of Acid                                                                             After Added to                                                                           Filtration                                                                          in the                          used to                                                                            State in Liquid                                                                           Treatment                                                                           in Liquid                                                                           Treatment                                                                           Base-                                                                              ppm Moly                                                                            Base-                           Dissolve                                                                           After After (% of After (% of Treated                                                                            Remaining                                                                           Treated                   NB Run #                                                                            Base Treatment                                                                           Treatment                                                                           Feed) Treatment                                                                           Feed) Peroxide                                                                           in Solution                                                                         Peroxide                  __________________________________________________________________________    6333-11                                                                             None Solids/                                                                             164.22                                                                              98.7  .003476                                                                              5.9  349.0                                                                               79.0 22.6                                 Filtered                                                           6333-13                                                                             None Solids/                                                                             160.02                                                                              96.1  .027487                                                                             46.4  346.0                                                                              210.0 60.7                                 Filtered                                                           6333-15                                                                             197.15                                                                             Solids/                                                                             162.52                                                                              97.6  .031548                                                                             53.2  308.0                                                                              160.0 51.9                            (TBA)                                                                              Filtered                                                           6333-12                                                                             None Clear 161.60                                                                              97.1  .026133                                                                             44.1  346.0                                                                               16.0  4.6                      6333-14                                                                              46.70                                                                             Clear 163.00                                                                              97.9  .024581                                                                             41.5  333.3                                                                              <10.0 <3.0                            (TBA)                                                                   6333-34                                                                             None Clear 162.25                                                                              97.5  .047172                                                                             79.6  340.0                                                                               14.0  4.1                      6333-35                                                                             None Solids/                                                                             162.44                                                                              97.6  .027373                                                                             46.2  348.0                                                                              349.0 100.3                                Filtered                                                           6333-36                                                                             None Solids/                                                                             161.88                                                                              97.3  .040969                                                                             69.1  344.0                                                                              349.0 101.4                                Filtered                                                           __________________________________________________________________________     In the basetreated peroxidates where solids formed upon base treatment,       the solids were filtered before moly was added.                          

Turning now to Table III, the most complete removal of acid contaminantswas obtained with sodium carbonate, in Run No. 6333-11, in that thesodium carbonate precipitated about 95% of the total acids present inthe feedstock. In this run an equivalent amount of base was fed relativeto the amount of acid present. In runs 6333-13, 6333-15, 6333-12,6333-14, 6333-34, 6333-34, 6333-35 and 6333-36 only 0.5 equivalent ofbase was used per equivalent of acid in the feed to be treated.Therefore, the expected amount of acids remaining in the liquid shouldbe 50% of that fed. In fact the average amount of acid left in theliquid in the last seven runs, (Table III-B column 17) is 54.32%. Thus,significantly larger percentages of the acid contaminants remained inthe liquid after treatment with the other basic reagents used, rangingfrom about 41.5% to about 79.6%, and constituting only about 69% for RunNo. 6333-36 wherein calcium oxide was used, and about 46% for Run No.6333-35 wherein calcium hydroxide was used.

Thus, as expected, the base treatment with about 1/2 equivalent of baseresulted in a partial purification of the feedstock in all instances.

However, note that when the molybdenum catalyst was added to thefiltrate, about 73% of the molybdenum prepcipitated from the filtrateresulting from treatment carbonate (Run No. 6333-11, Table III-B, column20). About half of the molybdenum precipitated from the filtrate whensodium hydroxide and sodium butoxide were used (Run No. 6333-13 and RunNo. 6333-15, respectively). In excess of 90% of the molybdenumprecipitated when potassium hydroxide, potassium butoxide and ammoniumhydroxide were used (Run No. 6333-12, Run No. 6333-14, and Run No.6333-34, respectively).

In contrast, when calcium oxide and calcium hydroxide were used, it wasfound, within the range of experimental error, that substantially all ofthe molybdenum remained in the filtrate (Run No. 6333-35 and Run No.6333-36). In other words, treatment of an acidic tertiary butyl alcoholsolution of tertiary butyl hydroperoxide with 1/2 of an equivalent ofcalcium oxide or calcium hydroxide, basis the acidity of the tertiarybutyl alcohol solution of tertiary butyl hydroperoxide, followed byfiltration of the solids, afforded a filtrate which did not precipitatethe molybdenum catalyst to be used in the epoxidation reaction. In bothof runs 6333-35 and 6333-36, the analysis indicated that slightly morethan 100% of the charged molybdenum remained in solution in thefiltrate. These numerical values are numbers obtained within the rangeof experimental accuracy.

Preparation of Olefin Epoxide using the Present Invention EXAMPLE 9Preparation of Moly Catalyst 5990-39-2 Moly EG Catalyst

To a 500-ml round bottomed flask equipped with a magnetic stirrer,thermometer, K-head, and condenser was added 196.2 g of ethylene glycol(3.164 moles) and 53.80 g of ammonium dimolybdate (0.3165 g atoms moly).The mole ratio of ethylene glycol to gram atoms of moly was 10/1. Thereaction mixture was padded with nitrogen and heated to 100° C. withstirring and held at 100° C. for 1.0 hour. The reaction mixture wascooled to 85° C. and a vacuum of 45 mm was pulled. The reaction mixture(under vacuum of 45 mm) was heated to 100° C. and held at 100° C. (30 mmvacuum) for 10 minutes and then cooled. The reaction mixture was lightyellow in color and solids free. The overhead weighed 12.0 grams (47.45%water) and the cold trap weighed 1.6 grams (89.44% water). The strippedproduct catalyst weighed 231.6 grams (92.64% of the total charge). Theproduct was analyzed and found to contain 13.0% molybdenum (atomicabsorption spectroscopy), 1.00% nitrogen, 0.74% water and have an acidnumber of 152.69 mgKOH/g sample.

EXAMPLE 10 Epoxidation of Octene-1 with Base Treated Peroxidate(6333-47)

100.0 g Peroxidate (6333-4-1) was found to contain 0.019750 moles acid(acid #=11.08 mgKOH/g) so it was treated with 0.585 g Ca(OH)₂ (MW=74.1,equiv. wt.=37.05, 0.0158 equivalents of base or 80% of the acidpresent). The peroxidate and Ca(OH)₂ were allowed to stir for severaldays at room temperature. The base-treated peroxidate was filtered andanalyzed and found to contain 55.15% TBHP (balance TBA), and had an acid#of 4.17 mgKOH/g sample. To 34.3 g of the base-treated and filtered TBHP(TBHP=55.15%, and acid #=4.17 mgKOH/g sample) was added 0.154 g ofmoly-EG catalyst (5990-39-2, 13.0% moly) in a 250 ml round-bottomedflask equipped with a mechanical stirrer, thermometer, N₂ pad, andcondenser. To the TBHP-moly EG catalyst solution was added 45.7 g of1-octene (Aldrich). The reaction mixture was heated to 95° C. and heldthere 2.0 hours. Product weighed 80.1 grams.

Analysis of the reaction mixture found % TBHP=3.54% and ppm moly=271.##EQU1##

The foregoing examples are given by way of illustration only and are notintended as limitations on the scope of this invention as defined by theclaims appended hereto.

We claim:
 1. In a method wherein isobutane is reacted with oxygen toprovide a reaction product comprising unreacted isobutane, tertiarybutyl hydroperoxide, tertiary butyl alcohol and carboxylic acidimpurities, including formic acid, acetic acid and isobutyric acid, theimprovement for at least partially purifying said reaction product whichcomprises the steps of:a. charging said reaction product to adistillation zone and separating it therein into at least a lighterisobutane fraction and a heavier distillation fraction comprisingtertiary butyl hydroperoxide, tertiary butyl alcohol and carboxylic acidimpurities, including formic acid, acetic acid and isobutyric acid, b.charging said heavier distillation fraction to a neutralization zone andtreating said heavier distillation fraction therein with about 1/2 to 1equivalent of calcium hydroxide or calcium oxide or a mixture of calciumhydroxide with calcium oxide, based on the carboxylic acid content ofsaid heavier distillation fraction to thereby provide a slurry of solidprecipitate in said thus-treated heavier distillation fraction, c.charging said slurry to a separation zone and separating it therein intoa solids fraction and a liquid filtrate fraction comprising saidpartially purified heavier distillation fraction comprising tertiarybutyl hydroperoxide, and tertiary butyl alcohol, and d. recovering saidfiltrate, whereby, use of said filtrate as a feed component in anepoxidation reaction wherein an olefin is reacted with tertiary butylhydroperoxide in solution in tertiary butyl alcohol in the presence of asoluble molybdenum catalyst will not cause molybdenum to precipitatefrom said solution.
 2. A method as in claim 1 wherein said initialreaction product contains from about 50 to about 80 wt. % of isobutane,from about 25 to 55 wt. % of tertiary butyl hydroperoxide, from about 25to about 55 wt. % of tertiary butyl alcohol and about 0.05 to about 2wt. % of said carboxylic acid impurities.
 3. A method as in claim 2wherein said heavier distillation fraction is treated with about 1/2equivalent of calcium hydroxide or calcium oxide, based on thecarboxylic acid content of said heavier distillation fraction.
 4. Amethod as in claim 3 wherein said heavier distillation fraction istreated with calcium oxide.
 5. A method as in claim 3 wherein saidheavier distillation fraction is treated with calcium hydroxide.